<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width">
    <link rel="stylesheet" href="css/download.css">
    <script src="jquery-2.2.3.js"></script>
    <title>下载</title>
</head>
<body>
<div id="wrapper">
    <div><img src="images/d-1.png" alt=""></div>
    <div>
        <a href=""><p>立即下载</p></a>
    </div>
</div>
</body>
</html>
<script>
    $(function(){
        function fullwidth(){
            if($('body').width() >= 720){
                $('html').css('font-size', 100 + 'px');
                return;
            }
            var scale = $('body').width() / 720;
            $('html').css('font-size',scale * 100 + 'px');
        }
        fullwidth();
        $(window).resize(function(){
            fullwidth();
        })
    });
</script>